Multi-speed power tool transmission with alternative ring gear configuration

ABSTRACT

A power tool with a housing, a multi-speed transmission and a switch mechanism. The switch mechanism has an actuator, a rail, a switch and first and second springs. The actuator is movable along a longitudinal axis of the transmission between a plurality of positions and is engaged to one or more members of the transmission at each of the plurality of actuator positions such that the transmission operates in a corresponding one of a plurality of different overall speed reduction ratios. The actuator is non-rotatably but axially slidably engaged to the housing. The rail is fixedly coupled to the actuator and is received through the switch such that the switch is mounted on the rail for sliding movement thereon. The first spring is disposed between the actuator and the switch and biases the switch away from the actuator. The second spring is disposed between the switch and an end of the rail opposite the actuator and biases biasing the switch away from the end of the rail.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/112,741 filed Nov. 8, 2008, the disclosure of which is herebyincorporated by reference as if fully set forth in detail herein.

INTRODUCTION

The present disclosure generally relates to power tools such asrotatable drill/drivers, hammer drill/drivers, hammer drills,screwdrivers, rotary hammers and rotatable cutting devices. Moreparticularly, the present disclosure relates to a multi-speedtransmission, a switching mechanism and a mode change mechanism for apower tool.

A power tool is described in U.S. Pat. Nos. 6,431,289 and 7,314,097.These power tools employ a three-speed transmission and a switchingmechanism. Additionally, the '097 patent employs a mode changemechanism. While such power tools are relatively robust, compact andinexpensive, there nonetheless remains a need in the art for an improvedpower tool that incorporates an improved multi-speed transmission,switching mechanism and/or mode change mechanism.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

In one form, the present teachings provide a power tool that includes ahousing, a motor, a trigger, an output spindle, a multi-speedtransmission and a switch mechanism. The housing defines a handle and abody into which the motor is received. The trigger is mounted to thehandle and is coupled to the motor. The trigger is configured to controloperation of the motor in response to an input provided by an operatorof the power tool by coupling the motor to a source of power. Themulti-speed transmission couples the motor and the output member. Theswitch mechanism includes an actuator, a rail, a switch, a first biasingspring, and a second biasing spring. The actuator is movable along alongitudinal axis of the multi-speed transmission between a plurality ofpositions. The actuator is engaged to one or more members of themulti-speed transmission at each of the plurality of actuator positionssuch that the multi-speed transmission operates in a corresponding oneof a plurality of different overall speed reduction ratios. The actuatoris non-rotatably but axially slidably engaged to the housing. The railis fixedly coupled to the actuator and is received through the switchsuch that the switch is mounted on the rail for sliding movementthereon. The first biasing spring is disposed between the actuator andthe switch and biases the switch away from the actuator. The secondbiasing spring is disposed between the switch and an end of the railopposite the actuator and biases the switch away from the end of therail.

In another form, the present teachings provide a power tool with ahousing, a motor, a trigger, an output member, a multi-speedtransmission and a switch mechanism. The housing defines a handle and abody into which the motor is received. The trigger is mounted to thehandle and coupled to the motor. The trigger is configured to controloperation of the motor in response to an input provided by an operatorof the power tool by coupling the motor to a source of power. Themulti-speed transmission couples the motor and the output member. Theswitch mechanism has a switch and an actuator. The switch is movablebetween a first switch position, a second switch position, and a thirdswitch position. The actuator is non-rotatably but axially slidablydisposed in the housing between a first actuator position, a secondactuator position, and a third actuator position. The actuator isengaged to one or more members of the multi-speed transmission at eachof the first, second and third actuator positions such that themulti-speed transmission operates in a corresponding one of a pluralityof different overall speed reduction ratios. The multi-speedtransmission and the switch mechanism are configured such that: theactuator will move with the switch when the switch is moved from thesecond switch position to the third switch position, the switch can moverelative to the actuator when the switch is moved from the third switchposition to the second switch position or from the second switchposition to the first switch position, and the switch can move relativeto the actuator when the switch is moved from the first switch positionto the second switch position.

In still another form, the present teachings provide a power tool with ahousing, a motor, a trigger, an output member and a transmission. Thehousing defines a handle and a body into which the motor is received.The trigger is mounted to the handle and coupled to the motor. Thetrigger is configured to control operation of the motor in response toan input provided by an operator of the power tool by coupling the motorto a source of power. The transmission couples the motor and the outputmember. The transmission includes a first planetary stage and a secondplanetary stage. The first planetary stage includes a planet carrier anda plurality of planet gears. The planet carrier includes a plurality ofpins onto which the planet gears are journally mounted. The secondplanetary stage comprises a sun gear having an outer diameter onto whicha plurality of sun gear teeth are formed. The pins of the planet carrierare mounted to the sun gear radially inward of the sun gear teeth and noportion of the sun gear that transmits torque is bigger in diameter thanthe outside diameter of the sun gear as measured across the sun gearteeth.

In still another form, the present teachings provide a power tool with ahousing, a motor, a trigger, an output member and a transmission. Thehousing defines a handle and a body into which the motor is received.The trigger is mounted to the handle and coupled to the motor. Thetrigger is configured to control operation of the motor in response toan input provided by an operator of the power tool by coupling the motorto a source of power. The transmission couples the motor and the outputmember. The transmission includes a first planetary stage and a secondplanetary stage. The first planetary stage comprises a compound planetgear having a first ring gear, a second ring gear, and a first planetgear portion, which is meshingly engaged to the first ring gear, and asecond planet gear portion that is coupled for rotation with the firstplanet gear portion and meshingly engaged with the second ring gear. Thesecond planetary stage comprises a third ring gear that is axiallymovable between a first position, in which the third ring gear ismeshingly engaged with a rotating component of the transmission, and asecond position in which the third ring gear is disengaged from therotating component.

In still another form, the present teachings provide a power tool with ahousing, a motor, a trigger, an output member and a transmission. Thehousing defines a handle and a body into which the motor is received.The trigger is mounted to the handle and coupled to the motor. Thetrigger is configured to control operation of the motor in response toan input provided by an operator of the power tool by coupling the motorto a source of power. The transmission couples the motor and the outputmember. The transmission includes a planetary stage having compoundplanetary gears with a first portion that is engaged to a first ringgear and a second portion that is engaged to a second ring gear. Thecompound planetary gears are not timed to another gear in thetransmission.

In still another form, the present teachings provide a power tool with ahousing, a motor, a trigger, an output member and a transmission. Thehousing defines a handle and a body into which the motor is received.The trigger is mounted to the handle and coupled to the motor. Thetrigger is configured to control operation of the motor in response toan input provided by an operator of the power tool by coupling the motorto a source of power. The transmission couples the motor and the outputmember. The transmission includes a planetary stage having a ring gear,a planet carrier and a plurality of planet gears. The planetary gearsare meshingly engaged with the ring gear and journally supported on pinsof the planet carrier. Adjacent ones of the pins are spaced apart by anangular spacing. Two or more different angular spacings are employed tothereby space the planet gears unevenly about the ring gear.

In still another form, the present teachings provide a power tool with ahousing, a motor, a trigger, an output member and a transmission. Thehousing defines a handle and a body into which the motor is received.The trigger is mounted to the handle and coupled to the motor. Thetrigger is configured to control operation of the motor in response toan input provided by an operator of the power tool by coupling the motorto a source of power. The transmission couples the motor and the outputmember. The power tool also includes a mode change mechanism having acam, a cam follower, a planet gear and a ring gear. The cam is rotatablymounted in the housing, while the cam follower is engaged to the cam andnon-rotatably but axially slidably mounted in the housing. The planetgear is meshingly engaged with the ring gear and teeth formed on thecam. Rotation of the ring gear generates corresponding rotation or thecam to cause axial translation of the cam follower in the housing. Thecam follower is employed to selectively lock-out a torque clutch,position an axially movable hammer ratchet into a zone where it may beengaged by a rotary hammer ratchet that is mounted on the outputspindle, or both.

In still another form, the present teachings provide a power tool with ahousing, a motor, a trigger, an output member and a transmission. Thehousing defines a handle and a body into which the motor is received.The trigger is mounted to the handle and coupled to the motor. Thetrigger is configured to control operation of the motor in response toan input provided by an operator of the power tool by coupling the motorto a source of power. The transmission couples the motor and the outputmember. The power tool also includes a spindle lock with a bushing thatis coupled to an output member of the transmission at a first interfaceand to the output spindle at a second interface. At least one of thefirst and second interfaces is defined by a female portion and a maleportion that is received in the female portion. The female portionincludes a plurality of first V-shaped sidewalls that have peaks thatface radially inwardly, while the male portion comprising a plurality ofsecond V-shaped sidewalls that are engaged the first V-shaped sidewalls.Each of the first V-shaped sidewalls is defined by a first interiorangle, and each of the second V-shaped sidewalls being defined by asecond interior angle that is smaller than the first interior angle torotationally couple the female portion and male portion in a manner thatprovides limited rotational movement there between.

In still another form, the present teachings provide a power tool with ahousing, a motor, a trigger, an output member and a transmission. Thehousing defines a handle and a body into which the motor is received.The trigger is mounted to the handle and coupled to the motor. Thetrigger is configured to control operation of the motor in response toan input provided by an operator of the power tool by coupling the motorto a source of power. The transmission couples the motor and the outputmember. The power tool further includes a clutch having a plurality offollower members and a clutch spring. The follower members are receivedbetween a clutch profile on a ring gear of the transmission and theclutch spring. The clutch spring biases the follower members intoengagement with the clutch profile. The clutch spring is an annular wavespring having a non-linear spring rate and preferably, a non-linearspring rate in which a plot depicting a load exerted by the clutchspring as a function of clutch spring deflection has a distinct kneebetween a first portion, which is generally defined by a first springrate, and a second portion that is generally defined by a second springrate that is greater than the first spring rate.

In still another form, the present teachings provide a power tool with ahousing, a motor, a trigger, an output member and a transmission. Thehousing defines a handle and a body into which the motor is received.The trigger is mounted to the handle and coupled to the motor. Thetrigger is configured to control operation of the motor in response toan input provided by an operator of the power tool by coupling the motorto a source of power. The transmission couples the motor and the outputmember. The power tool further includes a torque clutch and a clutchbypass member. The torque clutch includes a clutch profile, which iscoupled to a ring gear of the transmission, and a follower member thatis biased into engagement with the clutch profile to resist rotation ofthe ring gear when a magnitude of the torque output from the power tooldoes not exceed a clutch torque. The clutch bypass member includes aplurality of lugs that are non-rotatably but slidably engaged to thehousing. The clutch bypass member is axially movable between a firstposition, in which lugs are axially separated from the ring gear, and asecond position in which the lugs are received within the ring gear suchthat the lugs are positioned radially inwardly of the clutch profile.

In yet another form, the present teachings provide a power tool with ahousing, a motor, a trigger, an output member and a transmission. Thehousing defines a handle and a body into which the motor is received.The trigger is mounted to the handle and coupled to the motor. Thetrigger is configured to control operation of the motor in response toan input provided by an operator of the power tool by coupling the motorto a source of power. The transmission couples the motor and the outputmember. The transmission includes a planetary stage having a ring gear,the ring gear being axially movable between a first position and asecond position to cause a change in a speed ratio of the transmission,the power tool further comprising a spring that is mounted coaxiallyabout the transmission to bias the ring gear into one of the first andsecond positions

I a further form, the present teachings provide a power tool with ahousing, a motor, a trigger, an output member and a transmission. Thehousing defines a handle and a body into which the motor is received.The trigger is mounted to the handle and coupled to the motor. Thetrigger is configured to control operation of the motor in response toan input provided by an operator of the power tool by coupling the motorto a source of power. The transmission couples the motor and the outputmember. The housing includes a gear case, which houses at least aportion of the transmission, and a handle housing, which houses themotor. A plurality of features are formed onto the handle housing andthe gear case to align the two to a common rotary axis. The features cancomprise mating frusto-conically shaped surfaces.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustrative purposes only and arenot intended to limit the scope of the present disclosure in any way.The drawings are illustrative of selected teachings of the presentdisclosure and do not illustrate all possible implementations. Similaror identical elements are given consistent identifying numeralsthroughout the various figures.

FIG. 1 is a side elevation view of an exemplary power tool constructedin accordance with the teachings of the present disclosure;

FIG. 2 is an exploded perspective view of a portion of the power tool ofFIG. 1;

FIG. 3 is a perspective view of a portion of the power tool of FIG. 1illustrating the gear case and transmission assembly in more detail;

FIG. 4 is a perspective view of a portion of the transmission assemblyillustrating the input stage in more detail;

FIG. 5 is an exploded perspective view of the input stage of thetransmission assembly;

FIG. 6 is an exploded perspective view of the intermediate stage of thetransmission assembly;

FIG. 7 is an exploded perspective view of an output stage of thetransmission assembly;

FIG. 8 is an exploded perspective view of a portion of the power tool ofFIG. 1 illustrating portions of a clutch mechanism, a hammer mechanismand a mode change mechanism in more detail;

FIG. 9 is an elevation view of a portion of the input stage illustratingthe spacing of the compound planetary gears;

FIG. 10 is an exploded perspective view of a portion of the power toolof FIG. 1 illustrating the speed selector in more detail;

FIG. 11 is a longitudinal section view of a portion of the power tool ofFIG. 1;

FIGS. 12 through 15 are schematic representations of the transmissionassembly, illustrating the collar of the speed selector in variouspositions;

FIG. 16 is a schematic illustration of a portion of the clutch mechanismillustrating a wave spring having three distinct sections;

FIG. 17 is a lateral cross-section taken through the power tool of FIG.1 and illustrating a portion of the mode change mechanism;

FIG. 18 is an exploded perspective view of a portion of the mode changemechanism;

FIG. 19 is a perspective section view of a portion of the power tool ofFIG. 1 illustrating the construction of the gear case in more detail;

FIGS. 20, 21 and 22 illustrate portions of the mode change mechanism ofFIG. 18 and depict the relative positioning of the mode selection camplate, the clutch bypass member, the hammer activation member and thesecond cam when the mode collar is moved to first, second and thirdpositions, respectively;

FIGS. 23 and 24 are sectional views of a portion of the power tool ofFIG. 1 illustrating the mode change mechanism in more detail;

FIG. 25 is a plot illustrating load exerted by the clutch spring as afunction of its compression; and

FIG. 26 is a section view of a portion of the tool of FIG. 1,illustrating portions of the housing and the gear case.

DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS Overview

With reference to FIGS. 1 and 2 of the drawings, a power toolconstructed in accordance with the teachings of the present disclosureis generally indicated by reference numeral 10. As those skilled in theart will appreciate, such power tool 10 may be either a corded orcordless (battery operated) device, such as a portable screwdriver,drill/driver, hammer drill/driver or rotary hammer, for example. In theparticular embodiment illustrated, power tool 10 is a cordless hammerdrill/driver having a housing 12, a motor assembly 14, a multi-speedtransmission assembly 16, a clutch mechanism 18, an output spindle 20(FIG. 8), a hammer mechanism 22, a mode change mechanism 24, a chuck 26,a trigger assembly 28 and a battery pack 30.

The housing 12 can include a pair of mating housing shells 40 and a gearcase 42. The housing shells 40 can cooperate to define a handle portion44 and a body portion 46. The handle portion 44 can include a batterypack mount 48, to which the battery pack 30 can be removably coupled,and a switch mount 50. The trigger assembly 28, which can include atrigger 52 and a trigger switch 54, and be coupled to the switch mount50. The body portion 46 can define a motor cavity 56. The motor assembly14, which can include a rotatable output shaft 58, can be received inthe motor cavity 56. The gear case 42 can include a rear case portion60, a front case portion 62 and an annular wall member 64 that cancouple the rear and front case portions 60 and 62 to one another. Therear case portion 60 can be removably coupled to the housing shells 40via a plurality of fasteners (not specifically shown) to close a frontend of the body portion 46.

With reference to FIGS. 2 and 26, the housing shells 40 and the gearcase 42 having mating conically shaped features in the example providedthat aid in controlling alignment of the gear case 42 relative to thehousing shells 40 such that the motor assembly 14 and the transmissionassembly 16 are aligned along a common rotational axis. The matingconically shaped features can comprise first and second cone portions40-1 and 40-2 and can be located in two or more locations along theinterface between the housing shells 40 and the gear case 42. In theexample provided, mating conically shaped features are incorporated intofour bosses that are employed to receive threaded fasteners 12-1 thatfixedly but removably couple the housing shells 40 to the gear case 42.The first cone portion 40-1 can define a first frusto-conical surface40-2 that can be received against a corresponding second frusto-conicalsurface 42-2 that is formed into or onto the gear case 42. It will beappreciated that while the first frusto-conical surface 40-2 isillustrated as being a male surface and the second frusto-conicalsurface 42-2 is illustrated as being a female surface, those of skill inthe art will appreciate that the first frusto-conical surface 40-2 couldbe a female surface and that the second frusto-conical surface 42-2could be a male surface in the alternative. The first and second coneportions 40-1 and 40-2 can be employed to locate the gear case 42relative to the housing shells 40 in two directions that areperpendicular to the common rotational axis, as well as radially aboutthe common rotational axis. The threaded fasteners 12-1 can be receivedin each of the bosses and threadably engaged to the housing shells 40 togenerate a clamping force that causes an axial end face 42-3 of the gearcase 42 to abut an axial end face 40-3 of the housing shells 40. In somesituations, the axial end face 42-3 of the gear case 42 can be spacedapart from the axial end face 40-3 of the housing shells 40 when thefirst and second cone portions 40-1 and 42-1 are abutted against oneanother. It is expected, however, that the clamp load generated by thethreaded fasteners 12-1 can deform the first cone portions 40-1 somewhatso that the axial end faces 40-3 and 42-3 can abut one another.

The transmission assembly 16 can be received between the motor assembly14 and the gear case 42 and can transmit rotary power between the outputshaft 58 of the motor assembly 14 and the output spindle 20 (FIG. 8),which can be supported for rotation in the gear case 42. The clutchmechanism 18 can be employed to selectively limit the torque that istransmitted through the transmission assembly 16 to the output spindle20. The hammer mechanism 22 can be coupled to the gear case 42 and theoutput spindle 20 and can be selectively employed to produce an axiallyreciprocating motion to the output spindle 20 when the power tool 10 isoperated. The mode change mechanism 24 can be coupled to the housing 12,the clutch mechanism 18 and the hammer mechanism 22 to selectivelycontrol the operation of the hammer mechanism 22 and/or to selectivelylock-out or bypass the clutch mechanism 18. The chuck 26 can be coupledto an end of the output spindle 20 opposite the transmission assembly16.

Those of skill in the art will appreciate that various components of thepower tool 10, such as the motor assembly 14, the chuck 26, the triggerassembly 28 and the battery pack 30, can be conventional in theirconstruction and operation and as such, need not be discussed insignificant detail herein. Reference may be made to a variety ofpublications for a more complete understanding of the construction andoperation of the conventional components of the power tool 10, includingU.S. Pat. Nos. 6,431,289; 7,314,097; 5,704,433; and RE37,905, thedisclosures of which are hereby incorporated by reference as if fullyset forth in detail herein.

Transmission Assembly

With reference to FIGS. 2 and 3, the transmission assembly 16 caninclude a multi-speed transmission, such as a reduction gearset assembly100, and a switching mechanism, such as a speed selector 102. Thereduction gearset assembly 100 can be received in the rear case portion60 of the gear case 42 and can be a multi-stage planetary transmissionthat can include an input stage 110, an intermediate stage 112, and anoutput stage 114.

With reference to FIGS. 1, 4 and 5, the input stage 110 can include afirst input sun gear 120, a second input sun gear 122, an inputreduction carrier 124, a first set of input planetary gears 126, asecond set of input planetary gears 128, a first input ring gear 130 anda second input ring gear 132. The first and second input sun gears 120and 122 can be unitarily formed and can be coupled for rotation with theoutput shaft 58 of the motor assembly 14. The first input sun gear 120can be meshingly engaged with the planetary gears of the first set ofinput planetary gears 126, while the second input sun gear 122 can bemeshingly engaged with the planetary gears of the second set of inputplanetary gears 128. In the particular example provided, the planetarygears of the first and second sets of input planetary gears 126 and 128are unitarily formed (i.e., each of the planetary gears of the first setof input planetary gears 126 is integrally formed with an associated oneof the planetary gears of the second set of input planetary gears 128)and will be referred to herein as a compound planet gear 134. Those ofskill in the art will appreciate from this disclosure, however, that theplanetary gears of the first and second sets of planetary gears 126 and128 can be separately formed. The input reduction carrier 124 caninclude a first plate member 140, a second plate member 142 and aplurality of shafts 144 that extend between and couple the first andsecond plate members 140 and 142 to one another. Each of the compoundplanetary gears 134 can be journally supported on an associated one ofthe shafts 144. In the example provided, the quantity of the shafts 144is greater than the quantity of the compound planetary gears 134 and the“extra” shafts 144 are employed to better secure the first and secondplate members 140 and 142 to one another. The first input ring gear 130can include a first set of internal teeth 150, which can be meshinglyengaged to the planetary gears of the first set of input planetary gears126, and a first external engagement feature 152, such as a first set ofexternal teeth 154 that can be disposed about the outer diametricalsurface of the first input ring gear 130. Similarly, the second inputring gear 132 can include a second set of internal teeth 160, which canbe meshingly engaged to the planetary gears of the second set of inputplanetary gears 128 and a second external engagement feature 164, suchas a second set of external teeth 166 that can be disposed about anouter diametrical surface of the second input ring gear 132. In theparticular example provided, the quantity of teeth in the second set ofexternal teeth 166 is significantly less than the number of teeth in thefirst set of external teeth 154 as the second set of external teeth 166will carry less load (as will be apparent from the discussion, below).

With reference to FIGS. 5 and 6, the intermediate stage 112 can includean intermediate sun gear 180, an intermediate reduction carrier 182, aset of intermediate planetary gears 184 and an intermediate ring gear186. The intermediate sun gear 180 can be fixedly coupled to the inputreduction carrier 124 for rotation therewith. In the example provided,the intermediate sun gear 180 is integrally formed with the first platemember 140. The planetary gears of the set of intermediate planetarygears 184 can be meshingly engaged with the intermediate sun gear 180and the intermediate ring gear 186. The intermediate reduction carrier182 can include a first plate member 190, a second plate member 192 anda plurality of shafts 194 that extend between and couple the first andsecond plate members 190 and 192 to one another. Each of the planetarygears of the set of intermediate planetary gears 184 can be journallysupported on an associated one of the shafts 194. In the exampleprovided, the quantity of the shafts 194 is greater than the quantity ofthe planetary gears of the set of intermediate planetary gears 184 andthe “extra” shafts 194 are employed to better secure the first andsecond plate members 190 and 192 to one another. A third set of externalteeth 198 can be formed about the outer diameter of the first platemember 190 of the intermediate reduction carrier 182. The intermediatering gear 186 can include a third set of internal teeth 200, which canbe meshingly engaged to the planetary gears of the set of intermediateplanetary gears 184, and a third external engagement feature 202, suchas a fourth set of external teeth 204 that can be disposed about therear axial surface 206 of the intermediate ring gear 186.

With reference to FIG. 7, the output stage 114 can include an output sungear 220, an output reduction carrier 222, a set of output planetarygears 224 and an output ring gear 226. The output sun gear 220 can befixedly coupled to the intermediate reduction carrier 182 for rotationtherewith. In the example provided, the output sun gear 220 isintegrally formed with the second plate member 192 of the intermediatereduction carrier 182. The planetary gears of the set of outputplanetary gears 224 can be meshingly engaged with the output sun gear220 and the output ring gear 226. The output reduction carrier 222 caninclude a first plate member 230, a second plate member 232 and aplurality of shafts 234 that extend between and couple the first andsecond plate members 230 and 232 to one another. Each of the planetarygears of the set of output planetary gears 224 can be journallysupported on an associated one of the shafts 234. In the exampleprovided, the quantity of the shafts 234 is greater than the quantity ofthe planetary gears of the set of output planetary gears 224 and the“extra” shafts 234 are employed to better secure the first and secondplate members 230 and 232 to one another.

With additional reference to FIG. 8, the output spindle 20 can becoupled to the output reduction carrier 222 to transmit rotary powertherebetween. The output ring gear 226 can include an annular body 258,a fourth set of internal teeth 260, a plurality of clutch bypass lugs262 and a clutch profile 264 that will be described in more detail,below. The fourth set of internal teeth 260 can be formed about theinside diameter of the annular body 258 and can be meshingly engaged tothe planetary gears of the set of output planetary gears 224. The clutchbypass lugs 262 can extend radially inwardly from the annular body 258and can be circumferentially spaced apart around the annular body 258.The clutch bypass lugs 262 can include confronting surfaces 270 thatwill be discussed in more detail, below.

A spindle lock 250 can be disposed between the output reduction carrier222 and the output spindle 20 to lock the output spindle 20 againstrotation when torque is applied to the output spindle 20 from the chuck26 (FIG. 1) (i.e., as when the chuck 26 (FIG. 1) is being handtightened). The general construction of spindle locks are well known inthe art and as such, a detailed discussion of a spindle lock need not beprovided herein. In the particular example provided, the spindle lock250 comprises a spindle lock bushing 250-1 having a stem 250-2 thatextends rearwardly from a head 250-3. The stem 250-2 is configured toengage the second plate member 232 of the output reduction carrier 222in a slip-fit manner that permits limited relative rotationtherebetween. Similarly, the output shaft 20 can comprise a shaft end20-1 that can engage the spindle lock bushing 250-1 in a slip-fit mannerthat permits limited relative rotation therebetween. A matingmale-female configuration can be employed between the stem 250-2 and anaperture in the second plate member 232, as well as between an aperturein the spindle lock bushing 250-1 and the end 20-1 of the output spindle20. In each instance, the aperture can be shaped with two sets ofgenerally V-shaped sidewalls VS1 (FIG. 17) with each set being disposedopposite the other such that the peaks of the sets point toward oneanother, while the male portion inserted thereto can have correspondingV-shaped sidewalls VS2. It will be appreciated that the degree ofrelative rotation between the male and female portions (i.e., the stem250-2 and an aperture in the second plate member 232, and the aperturein the spindle lock bushing 250-1 and the end 20-1 of the output spindle20) can be configured based upon differences in the interior anglebetween the sets of the V-shaped sidewalls. For example, each set ofV-shaped sidewalls in a female feature (i.e., V-shaped sidewalls VS1)can be configured with a first interior angle, while each set ofV-shaped sidewalls in a male feature (i.e., V-shaped sidewalls VS2) canbe configured with a second, smaller interior angle. Configuration inthis manner permits the spindle lock 250 and output spindle 20 to have adesired degree of rotational backlash that is relatively easy tomaintain in high volume production without excessive cost.

Returning to FIG. 5, the second plate member 142 of the input reductioncarrier 124 is not a discrete component but rather is the intermediatesun gear 180 in the particular example provided. As such, the inputreduction carrier 124 does not include a flange that extends radiallyoutwardly of an associated sun gear as in the transmission that isdescribed in the '289 patent. Stated another way, the intermediate sungear 1870 has an outer diameter onto which a plurality of sun gear teethare formed and the pins 144 of the input reduction carrier 144 arecoupled to the intermediate sun gear 180 radially inwardly of the sungear teeth such that no portion of the intermediate sun gear 180 thattransmits torque during operation of the reduction gearset assembly 100(FIG. 2) is bigger in diameter than the outside diameter of theintermediate sun gear 180 as measured across the peaks of the sun gearteeth. Consequently, the pins 144 that support the planetary gears ofthe first and second sets of input planetary gears 126 and 128 can bedirectly coupled to an axial end face of the intermediate sun gear 180and one or both of the planetary gears associated with the first andsecond sets of input planetary gears 126 and 128 can have a pitchdiameter that is smaller in diameter than a pitch diameter of theintermediate sun gear 180.

While the planetary gears of the sets of first and second inputplanetary gears 126 and 128 can have any desired number of teeth, it maybe desirable in some instance to configure the planetary gears of theset of first input planetary gears 126 such that the quantity n1 oftheir teeth is a multiple of the quantity n2 of the teeth of theplanetary gears of the set of second input planetary gears 128. In thisregard a ratio of the quantity n1 to the quantity n2 can yield aninteger (e.g., 2, 3). This can be desirable as it can eliminate the needto time the planetary gears to one or more other geared elements of theinput stage 110 (or any other portion of the reduction gearset assembly100 (FIG. 2)), as well as permit the compound planetary gears 134 to beidentically formed (i.e., such that the planetary gears of the sets offirst and second input planetary gears 126 and 128 are maintained in thesame relative rotational orientation to one another). As will beappreciated, timing of gears involves the positioning of two or more ofthe gears into a predetermined rotational position relative to oneanother to permit engagement between predetermined teeth.

We have noted that in some situations, the space between the teeth ofthe planetary gears of the first set of input planetary gears 126 andthe first input ring gear 130 and/or the teeth of the planetary gears ofthe second set of input planetary gears 128 and the second input ringgear 132 that results from factors including intended clearance,tolerances and backlash can be sufficiently large so as to permit one ormore of the planetary gears of the sets of first and second inputplanetary gears 126 and 128 to be aligned one tooth out of phase withits associated ring gear (i.e., the first and second input ring gears130 and 132, respectively). While assembly fixtures could be employed toreduce or eliminate the possibility that the input stage 110 could bemisassembled, we discovered that it is also possible to make a slightalteration to the input stage 110 to shift the compound planetary gears134 in the manner that will be described in detail below so thatmisassembly of the input stage would not be possible.

With reference to FIGS. 5 and 9, the compound gears 134 (i.e., theplanetary gears of the first and second sets of input planetary gears126 and 128) can be distributed or circumferentially spaced apart in anydesired manner. While an even spacing can be employed in somesituations, an uneven spacing (i.e., as measured between shafts 144 ontowhich a compound planet gear 134 is received) was employed in theparticular example provided to reduce gear mesh noise that can beproduced when rotary power is transmitted through the reduction gearsetassembly 100 and to render it more difficult to misassemble the inputstage 110 of the reduction gearset assembly 100. As used herein, theterm “uneven spacing” is employed to refer to situations in which two ormore angular spacings are employed between adjacent planet gears in aplanetary stage. Accordingly, it will be appreciated that when unevenspacing is employed, at least one of the angular spacings will be equalto a first angular dimension and at least one angular spacing will beequal to a second angular dimension that is not equal to the firstangular dimension. It will also be appreciated that other angularspacings (e.g., a third angular spacing) could also be employed. In thespecific example provided, the four shafts 144 of the input reductioncarrier 124 on which the compound planetary gears 134 are mounted arespaced apart in the example provided by spacings of 92 degrees, 92degrees, 92 degrees and 84 degrees. Those of skill in the art willappreciate that other spacings could be employed and as such, the scopeof the present disclosure will not be understood to be limited to theparticular spacing or combination of spacings that are disclosed in theparticular example provided.

Returning to FIG. 3, as the transmission assembly 16 does not employ asleeve that is received between an exterior housing and a reductiongearset assembly (such a configuration is described in the '289 patent),the overall diameter of portions of the reduction gearset assembly 100,including the sets of first and second input planetary gears 126 and 128(FIG. 5), the set of intermediate planetary gears 184 (FIG. 6) and theset of output planetary gears 224 (FIG. 7), to be sized relativelylarger in diameter without increasing the overall diameter of the powertool. As a result of the increased diameter of the components of thereduction gearset assembly 100, corresponding decreases are achieved inthe torque applied to the various planetary gears as well as in the loadborne by the teeth of the various planetary gears. Consequently, it waspossible to reduce the overall length of the planetary gears of thereduction gearset assembly 100 to shorten the overall length of thereduction gearset assembly 100 relative to the transmission described inthe '289 patent by about 15 mm. It is within the scope of the presentdisclosure, however, to employ a sleeve between the reduction gearsetassembly 100 and the exterior housing.

Due in part to the enlarged diameter of the reduction gearset assembly100 and the shortened length of the planetary gears of the reductiongearset assembly 100, it was possible to enhance the efficiency of thereduction gearset assembly 100 through a reduction in the diameter ofthe pins 144 (FIG. 5), 194 (FIG. 6) and 234 (FIG. 7) of the variousreduction carriers 124 (FIG. 5), 182 (FIG. 6) and 222 (FIG. 7). In theparticular example provided, the pins 144 (FIG. 5), 194 (FIG. 6) and 234(FIG. 7) have a diameter of about 2.0 mm.

Returning to FIG. 10, the speed selector 102 can include a switchassembly 300 and an actuator assembly 302. The switch assembly 300 caninclude a switch 310; and a pair of first detent members 312, while theactuator assembly 302 can include a pair of rails 314; an actuator, suchas a collar 316; and first, second and third biasing springs 318, 320and 324, respectively.

The switch 310 can include a plate structure 330, a switch member 332, apair of second detent members 334 and a pair of bushings 336. The platestructure 330 can be received in pair of slots 340 (FIG. 1) formed intothe housing shells 40 generally parallel to a longitudinal axis 342 ofthe reduction gearset assembly 100 (FIG. 2). The switch member 332 canbe coupled to the plate structure 330 and can extend through a switchaperture 344 that can be defined by the housing shells 40. The switchmember 332 can be configured to receive a manual input from an operatorof the power tool 10 (FIG. 1) to move the switch 310 between a firstposition, a second position and a third position. Indicia (notspecifically shown) may be marked or formed on one or both of thehousing shells 40 or the plate structure 330 to indicate a position intowhich the switch 310 is located. The second detent members 334 cancooperate with the first detent members 312 to resist movement of theswitch 310. In the example provided, the second detent members 334comprise a plurality of detent recesses 348 that are formed in the platestructure 330. The bushings 336 can be coupled to the opposite lateralsides of the plate structure 330 and can include a bushing aperture 350and first and second end faces 352 and 354, respectively.

Each of the housing shells 40 can define a pair of detent mounts 360that can be configured to hold the first detent members 312. The firstdetent members 312 can be leaf springs having a raised protrusion 370and a pair of tabs 372. The detent mounts 360 can include a pair of tabrecesses 374, which can be configured to receive an associated one ofthe tabs 372, and a contoured platform 376 that can support the portionof the first detent member 312 disposed between the tabs 372. Thecontoured platform 376 can include a platform recess 378 into which theraised protrusion 370 may be moved when the switch 310 is moved betweenthe first, second and third positions. The raised protrusions 370 of thefirst detent members 312 are configured to engage an associated one ofthe detent recesses 348 that are formed in the plate structure 330

Each of the rails 314 can include a generally cylindrical rail body 380and a head portion 382 that can be relatively larger in diameter thanthe rail body 380. The rails 314 can be received through the bushingapertures 350 such that the bushings 336 are slidably mounted on therail bodies 380.

The collar 316 can be an annular structure that can include a pair ofmounts 400, an internal engagement feature 402, a fourth externalengagement feature 404 and a fifth external engagement feature 406. Anend of the rail bodies 380 opposite the head portions 382 can bereceived into the mounts 400 to fixedly couple the rails 314 to thecollar 316. In the particular example provided, the rail bodies 380 arepress-fit into the mounts 400, but it will be appreciated that othercoupling techniques, including bonding, adhesives, pins, and threadedfasteners, could be employed to couple the rails 314 to the collar 316.The internal engagement feature 402 can be formed about an innerdiameter of the collar 316 and can be sized to engage the first externalengagement feature 152 (FIG. 5) that is formed on the first input ringgear 130 (FIG. 5) and the second external engagement feature 164 (FIG.5) that is formed on the second input ring gear 132 (FIG. 5). In theparticular example provided, the internal engagement feature 402comprises a fifth set of internal teeth 410 that is configured to beengagable with the first set of external teeth 154 (FIG. 5) and thesecond set of external teeth 166 (FIG. 5). The fourth externalengagement feature 404 can comprise a set of external teeth or splines412 that can be slidingly engaged with corresponding internal teeth orsplines 414 that are coupled to (e.g., integrally formed with) the gearcase 42 as shown in FIG. 3. Returning to FIG. 10, the fifth externalengagement feature 406 can include a sixth set of external teeth 416that can be formed on a front axial surface 418 of the collar 316. Thefifth external engagement feature 406 can be selectively engaged withthe third external engagement feature 202 on the intermediate ring gear186 (i.e., the sixth set of external teeth 416 can be selectivelyengaged to the fourth set of external teeth 204) to couple the collar316 to the intermediate ring gear 186.

Each first biasing spring 318 can be mounted on an associated one of therail bodies 380 between the head portion 382 and the first end face 352of an associated one of the bushings 336. Each second biasing spring 320can be mounted on an associated one of the rail bodies 380 between thesecond end face 354 of an associated one of the bushings 336 and thecollar 316. With additional reference to FIG. 11, the third biasingspring 324 can be disposed between an annular lip 420 in the gear case42 and the front face 432 of the intermediate ring gear 186.

With reference to FIG. 12, the collar 316, the first input ring gear130, the second input ring gear 132, the intermediate reduction carrier182 and the intermediate ring gear 186 are schematically shown relativeto the longitudinal axis 342 of the reduction gearset assembly 100 (FIG.2) and the internal splines 414 that are coupled to the gear case 42. Itwill be appreciated that the collar 316 and the intermediate ring gear186 can move axially along the longitudinal axis 342.

With reference to FIGS. 2, 5 through 7 and 10, the reduction gearsetassembly 100 can be operated in a high speed ratio when the switch 310is located in the third position. In this position, the collar 316 canbe aligned relative to the first and second input ring gears 130 and 132and the intermediate ring gear 186 such that the internal engagementfeature 402 on the collar 316 is engaged with only the first externalengagement feature 152 on the first input ring gear 130 and the collar316 is axially spaced apart from the intermediate ring gear 186 so as tobe disengaged therefrom. In this condition, the first input ring gear130 is torsionally grounded (i.e., non-rotatably coupled) through thecollar 316 to the gear case 42, the second input ring gear 132 ispermitted to rotate, and the third biasing spring 324 biases theintermediate ring gear 186 rearwardly (i.e., in a direction toward themotor assembly 14) such that the third set of internal teeth 200 formedon the intermediate ring gear 186 are engaged with the third set ofexternal teeth 198 on the first plate member 190 of the intermediatereduction carrier 182. Accordingly, rotary power received from theoutput shaft 58 of the motor assembly 14 is input into the input stage110 via the first input sun gear 120. The first input sun gear 120, thefirst set of input planetary gears 126, the input reduction carrier 124and the first input ring gear 130 cooperate to perform a first inputspeed reduction and torque multiplication operation and to output afirst intermediate rotary output to the intermediate stage 112. Power isnot transmitted through the second input sun gear 122, the set of secondinput planetary gears 128 or the second input ring gear 132. Moreover,as the intermediate ring gear 186 is fixed for rotation with theintermediate reduction carrier 182, the intermediate stage 112 does notperform a speed reduction and torque multiplication function, but ratherprovides a second intermediate rotary output that is about equal inspeed and torque to the speed and torque of the first intermediaterotary output. Rotary power output from the intermediate stage 112 isreceived by the output stage 114, which performs a final speed reductionand torque multiplication operation and provides a final rotary outputthat is transmitted to the output spindle 20.

Operation in the high speed ratio is schematically illustrated in FIG.13 wherein the internal engagement feature 402 on the collar 316 isengaged to the first external engagement feature 152 on the first inputring gear 130 and the third set of external teeth 198 on theintermediate reduction carrier 182 are meshingly engaged to the thirdset of internal teeth 200 on the intermediate ring gear 186.

Returning to FIGS. 2, 5 through 7 and 10, the reduction gearset assembly100 can be operated in a medium speed ratio when the switch 310 islocated in the second position. In this position, the collar 316 canaligned relative to the first and second input ring gears 130 and 132and the intermediate ring gear 186 such that the internal engagementfeature 402 on the collar 316 is engaged with only the second externalengagement feature 164 on the second input ring gear 132 and the collar316 is axially spaced apart from the intermediate ring gear 186 so as tobe disengaged therefrom. In this condition, the second input ring gear132 is torsionally grounded (i.e., non-rotatably coupled) through thecollar 316 to the gear case 42, the first input ring gear 130 ispermitted to rotate, and the third biasing spring 324 biases theintermediate ring gear 186 rearwardly such that the third set ofinternal teeth 200 formed on the intermediate ring gear 186 are engagedwith the third set of external teeth 198 on the first plate member 190of the intermediate reduction carrier 182. Accordingly, rotary powerreceived from the output shaft 58 of the motor assembly 14 is input tothe input stage 110 via the second input sun gear 122. The second inputsun gear 122, the second set of input planetary gears 128, the inputreduction carrier 124 and the second input ring gear 132 cooperate toperform a second input speed reduction and torque multiplicationoperation and output the first intermediate rotary output to theintermediate stage 112. Those of skill in the art will appreciate thatthe speed and torque achieved through the second input speed reductionand torque multiplication operation are different from the speed andtorque achieved through the first input speed reduction and torquemultiplication operation. Power is not transmitted through the firstinput sun gear 120, the set of first input planetary gears 126 or thefirst input ring gear 130. Moreover, as the intermediate ring gear 186is fixed for rotation with the intermediate reduction carrier 182, theintermediate stage 112 does not perform a speed reduction and torquemultiplication operation, but rather provides a second intermediaterotary output that is about equal in speed and torque to the speed andtorque of the first intermediate rotary output. Rotary power output fromthe intermediate stage 112 is received by the output stage 114, whichperforms the final speed reduction and torque multiplication operationand provides a final rotary output that is transmitted to the outputspindle 20.

Operation in the medium speed ratio is schematically illustrated in FIG.14 wherein the internal engagement feature 402 on the collar 316 isengaged to the second external engagement feature 164 on the secondinput ring gear 132 and the third set of external teeth 198 on theintermediate reduction carrier 182 are meshingly engaged to the thirdset of internal teeth 200 on the intermediate ring gear 186.

With renewed reference to FIGS. 2, 5 through 7 and 10, the reductiongearset assembly 100 can be operated in a low speed ratio when theswitch 310 is located in the third position. In this position, thecollar 316 can aligned relative to the first and second input ring gears130 and 132 and the intermediate ring gear 186 such that the internalengagement feature 402 on the collar 316 is engaged with only the secondexternal engagement feature 164 on the second input ring gear 132 andthe collar 316 is abutted against the intermediate ring gear 186 todrive the intermediate ring gear 186 forwardly (i.e., toward the chuck26 (FIG. 1)). In this condition, the second input ring gear 132 istorsionally grounded through the collar 316 to the gear case 42, thefirst input ring gear 130 is permitted to rotate, and the collar 316 ispositioned to drive the intermediate ring gear 186 forwardly against thebias of the third biasing spring 324 such that the third set of internalteeth 200 formed on the intermediate ring gear 186 are disengaged fromthe third set of external teeth 198 on the first plate member 190 of theintermediate reduction carrier 182 and the third external engagementfeature 202 on the intermediate ring gear 186 is engaged to the fifthexternal engagement feature 406 on the collar 316 to thereby torsionallyground the intermediate ring gear 186 to the gear case 42 through thecollar 316. Accordingly, rotary power received from the output shaft 58of the motor assembly 14 is input to the input stage 110 via the secondinput sun gear 122. The second input sun gear 122, the second set ofinput planetary gears 128, the input reduction carrier 124 and thesecond input ring gear 132 cooperate to perform the second input speedreduction and torque multiplication operation and output the firstintermediate rotary output to the intermediate stage 112. Power is nottransmitted through the first input sun gear 120, the set of first inputplanetary gears 126 or the first input ring gear 130. Rotary power canbe received into the intermediate stage 112 through the intermediate sungear 180. The intermediate sun gear 180, the set of intermediateplanetary gears 184, the intermediate reduction carrier 182 and theintermediate ring gear 186 cooperate to perform an intermediate speedreduction and torque multiplication operation and output the secondrotary output to the output stage 114. Rotary power output from theintermediate stage 112 is received by the output stage 114, whichperforms the final speed reduction and torque multiplication operationand provides a final rotary output that is transmitted to the outputspindle 20.

Operation in the low speed ratio is schematically illustrated in FIG. 15wherein the internal engagement feature 402 on the collar 316 is engagedto the second external engagement feature 164 on the second input ringgear 132, the third set of external teeth 198 on the intermediatereduction carrier 182 are disengaged from the third set of internalteeth 200 on the intermediate ring gear 186, and the fifth externalengagement feature 406 on the collar 316 is engaged to the thirdexternal engagement feature 202 on the intermediate ring gear 186.

Returning to FIG. 10, it will be appreciated that the first and secondbiasing springs 318 and 320 are configured to resiliently couple thecollar 316 to the switch 310 in a manner that provides for a modicum ofcompliance.

In instances where the switch 310 is to be moved from the first positionto the second position but the second external engagement feature 164(FIG. 5) on the second input ring gear 132 (FIG. 5) is not aligned tothe internal engagement feature 402 on the collar 316, the switch 310can be translated into the second position without fully moving thecollar 316 by an accompanying amount. In such situations, the secondbiasing springs 320 are compressed between the second end face 354 ofthe bushings 336 and the mounts 400 of the collar 316. Rotation of thesecond input ring gear 132 (FIG. 5) relative to the collar 316 canpermit the second external engagement feature 164 (FIG. 5) to align tothe internal engagement feature 402 and once aligned, the second biasingspring 320 can urge the collar 316 forwardly into engagement with thesecond input ring gear 132 (FIG. 5).

In instances where the switch 310 is to be moved from the secondposition to the third position but the third external engagement feature202 (FIG. 6) on the intermediate ring gear 186 (FIG. 6) is not alignedto the fifth external engagement feature 406 formed on the collar 316,the switch 310 can be translated into the third position while fullymoving the collar 316 by an accompanying amount. In such situations, thesecond biasing springs 320 are not further compressed between the secondend face 354 of the bushings 336 and the mounts 400 of the collar 316but rather the third biasing spring 324 can be compressed when theintermediate ring gear 186 (FIG. 6) is driven relatively further forwarddue to contact between the axial end faces of the collar 316 and theintermediate ring gear 186 (FIG. 6). Rotation of the intermediate ringgear 186 (FIG. 6) relative to the collar 316 can permit the thirdexternal engagement feature 202 (FIG. 6) to align to the fourth externalengagement feature 404 and once aligned, the third biasing spring 324can urge the intermediate ring gear 186 (FIG. 6) rearward intoengagement with the collar 316.

In instances where the switch 310 is to be moved from the third positionto the second position but the third set of internal teeth 200 (FIG. 6)are not aligned to the third set of external teeth 198 (FIG. 6), theswitch 310 can be translated into the second position while fully movingthe collar 316 by an accompanying amount. In such situations, the thirdbiasing spring 324 can apply a rearwardly directed force onto theintermediate ring gear 186 (FIG. 6). Rotation of the intermediate ringgear 186 (FIG. 6) relative to the intermediate reduction carrier 182(FIG. 6) can permit the third set of internal teeth 200 (FIG. 6) toalign to the third set of external teeth 198 (FIG. 6) and once aligned,the third biasing spring 324 can urge the intermediate ring gear 186(FIG. 6) rearward such that the third set of internal teeth 200 (FIG. 6)are engaged to the third set of external teeth 198 (FIG. 6).

In instances where the switch 310 is to be moved from the secondposition to the first position but the internal engagement feature 402formed on the collar 316 is not aligned to the first external engagementfeature 152 (FIG. 5) formed on the first input ring gear 130 (FIG. 5),the switch 310 can be translated into the first position without fullymoving the collar 316 by an accompanying amount. In such situations, thefirst biasing springs 318 are compressed between the head portion 382 ofthe rails 314 and the first end face 352 of the bushings 336. Rotationof the first input ring gear 130 (FIG. 5) relative to the collar 316 canpermit the first external engagement feature 152 (FIG. 5) to align tothe internal engagement feature 402 and once aligned, the first biasingspring 318 can urge the collar 316 rearwardly into engagement with thefirst input ring gear 130 (FIG. 5).

Clutch Mechanism

With reference to FIGS. 8 and 11, the clutch mechanism 18 can includethe clutch profile 264, a clutch adjustment collar 500, a followerstructure 502 and a clutch spring 504. The clutch profile 264 can becoupled to (e.g., integrally formed on) a forwardly facing surface ofthe output ring gear 226. In the example provided, the clutch profile264 includes a plurality of tapered ramps and a plurality of valleysthat are disposed between an adjacent pair of the tapered ramps. Theclutch adjustment collar 500 can be rotatably mounted on the gear case42 and can conventionally include a clutch collar 510, which can berotatably mounted on the gear case 42, and a clutch nut 512 that can bethreadably engaged to an internally threaded portion 514 of the clutchcollar 510 and axially movably but non-rotatably coupled to the gearcase 42. In this way, rotation of the clutch collar 510 can be employedto effect corresponding translation of the clutch nut 512. The followerstructure 502 can include an annular follower body 520 and a pluralityof follower members 522. The follower body 520 can be mounted on thegear case 42 coaxially with the clutch adjustment collar 500. Thefollower members 522 can extend through holes 524 formed in the annularwall member 64 of the gear case 42 generally parallel to thelongitudinal axis 342 of the reduction gearset assembly 100. An end ofthe follower members 522 opposite the follower body 520 is configured toengage the clutch profile 264. In the particular example provided, thefollower members 522 include a plurality of bearing balls that arereceived between the follower body 520 and the clutch profile 264. Itwill be appreciated, however, that the follower members 522 could beintegrally formed with the follower body 520 or that other shapedfollower members 522 could be employed. The clutch spring 504 can bedisposed between the clutch nut 512 and the follower body 520 and isconfigured to exert a force on the follower structure 502 that istransmitted through the follower members 522 to the clutch profile 264.In the particular example provided, the clutch spring 504 is a wavespring having a non-linear spring rate, such as a non-linear spring ratethat produces a spring load versus spring deflection curve with adistinct knee K between a first portion P1, which is generally definedby a first spring rate, and a second portion P2 that is generallydefined by a second spring rate that is greater than the first springrate as depicted in FIG. 25. With specific reference to FIG. 16, theclutch spring 504 can include end sections 540 and a mid-section 542that is disposed between the end sections 540. Each of the end sections540 can be configured with a first spring rate, while the mid-section542 can be configured with a second spring rate that is higher than thefirst spring rate.

Returning to FIGS. 8 and 11, those of skill in the art will appreciatethat when a reaction torque acting on the output ring gear 226 exceeds aclutch torque that is set through adjustment of the clutch adjustmentcollar 500, the output ring gear 226 will rotate such that the taperedramps on the clutch profile 264 ride or cam over the follower members522. Such rotation of the output ring gear 226 effectively limits thetorque that is output from the transmission assembly 16 to the outputspindle 20.

Hammer Mechanism

With reference to FIG. 8, the hammer mechanism 22 can include a firstcam 600 and a second cam 602. The first cam 600 can include a pluralityof first tapered ramps 610 and can be coupled for rotation with theoutput spindle 20. The output spindle 20 is supported by the spindlelock 250 and one or more bearings (e.g., bearing 611) for axialtranslation and rotation. More specifically, inside surfaces 250 a and611 a of the spindle lock 250 and the bearing 611, respectively, engagethe output spindle 20 in a slip fit manner that permits the permits theoutput spindle 20 to translate along the longitudinal axis 342 of thereduction gearset assembly 100 (FIG. 2). Rearward translation of theoutput spindle 20 can be limited through contact between the outputspindle 20 and the gear case 42, while forward translation of the outputspindle 20 can be limited by contact between the bearing 611 and thegear case 42. The second cam 602 can include a plurality of secondtapered ramps 612, which can be configured to matingly engage the firsttapered ramps 610, and can be non-rotatably but axially movably mountedin the gear case 42.

The hammer mechanism 22 can be disengaged by positioning the second cam602 in a rearward position (by the mode change mechanism 24, as will bedescribed in greater detail, below) that is axially rearward of thefirst cam 600 by a distance that is sufficient to prevent engagementbetween the first and second cams 600 and 602 when the output spindle 20is pushed into its rearward most position. The hammer mechanism 22 canbe engaged by positioning the second cam 602 in a forward position (bythe mode change mechanism 24) where the first cam 600 can contact thesecond cam 602 when the output spindle 20 is pushed axially rearward. Asthe first cam 600 rotates with the output spindle 20 and the second cam602 is non-rotatably coupled to the gear case 42, the first taperedramps 610 of the first cam 600 can alternately engage and disengage thesecond tapered ramps 612 of the second cam 602 to cause axial movementof the output spindle 20 when the power tool 10 is operated and arearwardly directed force is applied to the output spindle 20.

Mode Change Mechanism

With reference to FIGS. 8 and 11, the mode change mechanism 24 caninclude a mode collar 700, an idler gear 702, a mode selection cam plate704, a clutch bypass member 706, a hammer activation member 708, abypass member biasing spring 710 and an activation member biasing spring712.

With reference to FIGS. 8 and 17, the mode collar 700 can be an annularstructure that can be received about the rear case portion 60 of thegear case 42 rearwardly of the clutch adjustment collar 500. The modecollar 700 can include a plurality of internal teeth 720, three modedetent recesses 722 and one or more mode tabs 724. The rear case portion60 of the gear case 42 can carry a mode detent 730 that can resilientlyengage the mode detent recesses 722 to inhibit relative rotation betweenthe mode collar 700 and the gear case 42. The mode tabs 724 can beconfigured to permit an operator to better grip and rotate the modecollar 700. Features, such as shallow tapered walls 740, can be formedin the rear case portion 60 and can contact the mode tabs 724 to limitrotation of the mode collar 700 relative to the gear case 42.

The idler gear 702 can be rotatably mounted on the gear case 42 and caninclude teeth that can be meshingly engaged to the internal teeth 720 onthe mode collar 700. In the example provided, an idler gear aperture isformed in the front case portion 62 of the gear case 42 and an axle 750is fitted through the idler gear 702 into the annular wall member 64 ofthe gear case 42.

With reference to FIGS. 8, 17, 18 and 23, the mode selection cam plate704 can be received in the front case portion 62 for rotation therein.The mode selection cam plate 704 can include a plurality of externalteeth 760, which can be meshingly engaged to the teeth of the idler gear702, a clutch bypass surface 770 and a hammer activation surface 772. Ahole 774 can be formed through the mode selection cam plate 704 throughwhich the output spindle 20 can be received. The clutch bypass surface770 can define a plurality of circumferentially spaced apart first lands780, a plurality of circumferentially spaced apart second lands 782, anda plurality of ramps 784, each of which connecting one of the firstlands 780 to an associated one of the second lands 782. The hammeractivation surface 772 can be disposed radially inwardly of the clutchbypass surface 770 and can define a plurality of circumferentiallyspaced apart third lands 790, a plurality of circumferentially spacedapart fourth lands 792 and a plurality of ramps 794, each of whichconnecting one of the third lands 790 to an associated one of the fourthlands 792.

The clutch bypass member 706 can include an annular body 800 and aplurality of lugs 802. The annular body 800 can define a central bore810, a plurality of guide ways 812 and a first cam follower 814. Theguide ways 812 can extend through the annular body 800 generallyparallel to a longitudinal axis of the central bore 810. The first camfollower 814 can be sized to engage the clutch bypass surface 770 on themode selection cam plate 704. The first cam follower 814 can include aplurality of first lands 820, a plurality of second lands 822, and aplurality of tapered ramps 824. Rotation of the mode selection cam plate704 into a first position can locate the second lands 822 on the annularbody 800 in abutment with the first lands 780 on the clutch bypasssurface 770 to position the clutch bypass member 706 in a forwardposition. Rotation of the mode selection cam plate 704 into a secondposition or a third position can locate the first and second lands 820and 822 in abutment with the first and second lands 780 and 782,respectively, as well as the tapered ramps 824 in abutment with thetapered ramps 784 such that the clutch bypass member 706 is disposed ina rearward position. The lugs 802 can be circumferentially spaced apartabout the exterior periphery of the annular body 800 and can extendrearwardly from the annular body 800 generally perpendicular to thelongitudinal axis of the central bore 810. The lugs 802 can have anydesired shape but in the particular example provided, have a shape thatcorresponds to a shape of a plurality of first guide passages 830 (FIG.17) formed in the front case portion 62 of the gear case 42. The firstguide passages 830 can be formed into a rear side of the front caseportion 62 radially outwardly of a central cylindrical surface 832 (FIG.19) and can terminate at an end wall 834 (FIG. 19). It will beappreciated that the lugs 802 can be disposed radially outwardly of themode selection cam plate 704 and that the central cylindrical surface832 (FIG. 19) can help to align a rotational axis of the mode selectioncam plate 704 to the longitudinal axis 342 of the reduction gearsetassembly 100 (FIG. 2). The first guide passages 830 can cooperate withthe lugs 802 to inhibit relative rotation between the clutch bypassmember 706 and the gear case 42, as well as to guide the clutch bypassmember 706 as it translates along an axis that is coincident with thelongitudinal axis 342 of the reduction gearset assembly 100 (FIG. 2).

The hammer activation member 708 can include an annular body 850 and aplurality of lugs 852 that can define a second cam follower 854. Theannular body 850 can define a central bore 856 into which the second cam602 can be received. The second cam 602 can be fixedly coupled to theannular body 850 through any appropriate means, including aninterference fit. The lugs 852 can be circumferentially spaced apartabout the exterior periphery of the annular body 850 and can extendrearwardly from the annular body 850 generally perpendicular to thelongitudinal axis of the central bore 856. The lugs 852 can have anydesired shape but in the particular example provided, have a shape thatcorresponds to a shape of the guide ways 812 in the annular body 800 ofthe clutch bypass member 706. The guide ways 812 can cooperate with thelugs 852 to inhibit relative rotation between the hammer activationmember 708 and the gear case 42, as well as to guide the hammeractivation member 708 as it translates along an axis that is coincidentwith the longitudinal axis 342 of the reduction gearset assembly 100(FIG. 2). The second cam follower 854 can be sized to engage the hammeractivation surface 772 on the mode selection cam plate 704. The secondcam follower 854 can include a plurality of third lands 860 and aplurality of tapered ramps 864. Rotation of the mode selection cam plate704 into the first position can locate the third lands 860 in abutmentwith the fourth lands 792, as well as the tapered ramps 864 in abutmentwith the tapered ramps 794 such that the hammer activation member 708 isdisposed in a rearward position. Rotation of the mode selection camplate 704 into a third position can locate the third lands 860 on theannular body 850 in abutment with the third lands 790 on the hammeractivation surface 772 to position the hammer activation member 708 in aforward position.

With reference to FIG. 8, the bypass member biasing spring 710 can bereceived between the front case portion 62 of the gear case 42 and theclutch bypass member 706 and can exert a rearwardly directed biasingforce onto the clutch bypass member 706. The activation member biasingspring 712 can be received between the front case portion 62 of the gearcase 42 and the hammer activation member 708 and can exert a rearwardlydirected biasing force onto the hammer activation member 708.

In operation, the mode collar 700 can be moved between a first modeposition, a second mode position and a third mode position to causecorresponding movement of the mode selection cam plate 704 between thefirst position, the second position and the third position,respectively.

With reference to FIGS. 8, 18 and 20 when the mode collar 700 isdisposed in the first mode position (i.e., the mode selection cam plate704 is in the first position), the clutch bypass member 706 can bedisposed in its forward position such that the lugs 802 of the clutchbypass member 706 are axially spaced apart (forwardly) from the clutchbypass lugs 262, while the hammer activation member 708 can be disposedin its rearward position such that the second cam 602 is axially spacedapart (rearwardly) from the first cam 600. In this condition, the clutchmechanism 18 is permitted to function in its normal manner (i.e., toresist rotation of the output ring gear 226 until the reaction torqueacting on the output ring gear 226 exceeds a user-selected clutchtorque) and the hammer mechanism 22 is deactivated.

With reference to FIGS. 8, 18 and 21, rotation of the mode collar 700from the first mode position to the second mode position can causecorresponding rotation of the mode selection cam plate 704 (via theidler gear 702) such that the mode selection cam plate 704 is positionedin its second position. Correspondingly, the clutch bypass member 706can be disposed in its rearward position such that the lugs 802 of theclutch bypass member 706 are disposed between adjacent ones of theclutch bypass lugs 262, while the hammer activation member 708 can bedisposed in its rearward position such that the second cam 602 isaxially spaced apart (rearwardly) from the first cam 600. In thiscondition, the hammer mechanism 22 is deactivated and the clutchmechanism 18 is bypassed so that the torque that is output from thepower tool 10 (FIG. 1) is not affected by the setting of the clutchmechanism 18. In instances where the torque reaction acting on theoutput ring gear 226 exceeds the user-selected clutch torque, the outputring gear 226 can rotate slightly to engage the confronting surfaces 270of the clutch bypass lugs 262 against the lugs 802 of the clutch bypassmember 706 to thereby arrest further rotation of the output ring gear226.

With reference to FIGS. 8, 18 and 22, rotation of the mode collar 700from the second mode position to the third mode position can causecorresponding rotation of the mode selection cam plate 704 (via theidler gear 702) such that the mode selection cam plate 704 is positionedin its third position. Correspondingly, the clutch bypass member 706 canremain in its rearward position such that the lugs 802 of the clutchbypass member 706 are disposed between adjacent ones of the clutchbypass lugs 262, while the hammer activation member 708 can be disposedin its forward position such that the second cam 602 is spaced proximatethe first cam 600 for the first ramps 784 to contact the second ramps784 when a rearwardly directed force is applied to the output spindle20. In this condition, the clutch mechanism 18 is bypassed as describedabove and the hammer mechanism 22 is activated.

It will be appreciated that the above description is merely exemplary innature and is not intended to limit the present disclosure, itsapplication or uses. While specific examples have been described in thespecification and illustrated in the drawings, it will be understood bythose of ordinary skill in the art that various changes may be made andequivalents may be substituted for elements thereof without departingfrom the scope of the present disclosure as defined in the claims.Furthermore, the mixing and matching of features, elements and/orfunctions between various examples is expressly contemplated herein,even if not specifically shown or described, so that one of ordinaryskill in the art would appreciate from this disclosure that features,elements and/or functions of one example may be incorporated intoanother example as appropriate, unless described otherwise, above.Moreover, many modifications may be made to adapt a particular situationor material to the teachings of the present disclosure without departingfrom the essential scope thereof. Therefore, it is intended that thepresent disclosure not be limited to the particular examples illustratedby the drawings and described in the specification as the best modepresently contemplated for carrying out the teachings of the presentdisclosure, but that the scope of the present disclosure will includeany embodiments falling within the foregoing description and theappended claims.

1. A power tool comprising: a housing defining a handle and a body; a motor received in the body; a trigger mounted to the handle and coupled to the motor, the trigger being adapted to control operation of the motor in response to an input provided by an operator of the power tool by coupling the motor to a source of power; an output member; a multi-speed transmission coupling the motor and the output member; and a switch mechanism comprising an actuator, a rail, a switch, a first biasing spring, and a second biasing spring, the actuator being movable along a longitudinal axis of the multi-speed transmission between a plurality of positions, the actuator being engaged to one or more members of the multi-speed transmission at each of the plurality of actuator positions such that the multi-speed transmission operates in a corresponding one of a plurality of different overall speed reduction ratios, the actuator being non-rotatably but axially slidably engaged to the housing, the rail being fixedly coupled to the actuator, the rail being received through the switch such that the switch is mounted on the rail for sliding movement thereon, the first biasing spring being disposed between the actuator and the switch and biasing the switch away from the actuator, the second biasing spring being disposed between the switch and an end of the rail opposite the actuator, the second biasing spring biasing the switch away from the end of the rail.
 2. The power tool of claim 1, wherein the rail is movable relative to the housing.
 3. The power tool of claim 2, wherein the switch is movable into at least three different switch positions, each switch position being associated with a corresponding one of the actuator positions.
 4. The power tool of claim 3, further comprising a third biasing spring, wherein the first, second and third biasing springs are employed to provide compliance between the actuator and the multi-stage transmission when the switch is moved between first, second and third switch positions but the actuator cannot be moved into an associated actuator position due to misalignment between the actuator and the one or more members of the multi-speed transmission.
 5. The power tool of claim 4, wherein the third biasing spring is disposed in a location that is axially separated from the rail, the switch, and the actuator.
 6. The power tool of claim 4, wherein the third biasing spring is mounted coaxially about the multi-speed transmission.
 7. The power tool of claim 1, wherein the actuator is an annular structure comprising at least one of a plurality of teeth formed about a circumferentially extending portion of the actuator and a plurality of teeth extending axially from a portion of the actuator.
 8. The power tool of claim 7, wherein the circumferentially extending portion of the actuator extends in an unbroken ring.
 9. The power tool of claim 1, wherein one of the housing and the switch carries a detent spring, wherein a plurality of detent recesses are formed into the other one of the housing and the switch, each detent recess being associated with a placement of the switch relative to the housing that is associated with a corresponding one of the actuator positions, each detent recess being engagable by the detent spring to resist relative axial movement between the switch and the housing.
 10. The power tool of claim 1, wherein the one or more members of the multi-speed transmission comprise ring gears.
 11. The power tool of claim 10, wherein the switch is movable between a first switch position, a second switch position and a third switch position, wherein the actuator is engagable to a first ring gear when the switch is disposed in the first switch position, wherein the actuator is engagable to a second ring gear when the switch is disposed in the second switch position, and wherein the actuator is engagable to the second ring gear and a third ring gear when the switch is in the third switch position.
 12. The power tool of claim 11, further comprising a third biasing spring that biases the third ring gear toward the second ring gear.
 13. The power tool of claim 12, wherein the third biasing spring biases the third ring gear into engagement with a planet carrier such that the third ring gear co-rotates with the planet carrier.
 14. The power tool of claim 1, wherein at least one of the first and second biasing springs is received coaxially on the rail.
 15. The power tool of claim 1, wherein at least one of the first and second biasing springs is a helical compression spring.
 16. The power tool of claim 1, wherein the housing comprises a first housing portion and a second housing portion, wherein the handle is defined by the first housing portion and wherein the first and second housing portions cooperate to define the body.
 17. A power tool comprising: a housing defining a handle and a body; a motor received in the body; a trigger mounted to the handle and coupled to the motor, the trigger being adapted to control operation of the motor in response to an input provided by an operator of the power tool by coupling the motor to a source of power; an output member; a multi-speed transmission coupling the motor and the output member; and a switch mechanism having a switch and an actuator, the switch being movable between a first switch position, a second switch position, and a third switch position, the actuator being non-rotatably but axially slidably disposed in the housing between a first actuator position, a second actuator position, and a third actuator position, the actuator being engaged to one or more members of the multi-speed transmission at each of the first, second and third actuator positions such that the multi-speed transmission operates in a corresponding one of a plurality of different overall speed reduction ratios; wherein the multi-speed transmission and the switch mechanism are configured such that: (a) the actuator will move with the switch when the switch is moved from the second switch position to the third switch position; (b) the switch can move relative to the actuator when the switch is moved from the third switch position to the second switch position or from the second switch position to the first switch position; and (c) the switch can move relative to the actuator when the switch is moved from the first switch position to the second switch position.
 18. The power tool of claim 17, wherein the switch mechanism includes a pair of rails that are fixed to the actuator and wherein the switch is slidably mounted on the pair of rails.
 19. The power tool of claim 18, wherein the actuator comprises an annular structure that is selectively engagable with a plurality of geared members in the multi-speed transmission.
 20. A power tool comprising: a housing defining a handle and a body; a motor received in the body; a trigger mounted to the handle and coupled to the motor, the trigger being adapted to control operation of the motor in response to an input provided by an operator of the power tool by coupling the motor to a source of power; an output member; a multi-speed transmission coupling the motor and the output member, the multi-speed transmission comprising a first stage and a second stage, the first stage comprising a first sun gear, a plurality of compound planet gears, a first ring gear and a second ring gear, the first sun gear being driven by the motor and meshingly engaged with the compound planet gears, each compound planet gear having a first planet gear portion, which is meshingly engaged to the first ring gear, and a second planet gear portion that is fixed to the first planet gear portion for rotation therewith and meshingly engaged to the second ring gear, the second stage comprising a third ring gear that is axially movable between an inactive position, in which the third ring gear is engaged with a rotary member of the multi-speed transmission such that the third ring gear and the rotary member co-rotate, and an active position in which the third ring gear is disengaged from the rotary member; and a speed selector comprising a switch, an actuator, a first biasing spring, a second biasing spring and a third biasing spring, the switch being movable between a first switch position, a second switch position, and a third switch position, the actuator being non-rotatably but axially slidably disposed in the housing between a first actuator position, a second actuator position, and a third actuator position, the actuator being engaged to one or more members of the multi-speed transmission at each of the first, second and third actuator positions such that the multi-speed transmission operates in a corresponding one of a plurality of different overall speed reduction ratios; wherein the first biasing spring biases the actuator toward the switch when the switch is in the second position and the actuator is disposed between the third and second actuator positions; wherein the first biasing spring biases the actuator toward the switch when the switch is in the first position and the actuator is disposed between the second and first actuator positions; wherein the second biasing spring biases the actuator biasing the actuator away from the switch when the switch is in the second switch position and the actuator is disposed between the first and second actuator positions; and wherein the third biasing spring biases the third ring gear toward the actuator when the switch is in the third switch position, the actuator is in the third actuator position and the actuator is not engaged to the third ring gear.
 21. A power tool comprising: a housing defining a handle and a body; a motor received in the body; a trigger mounted to the handle and coupled to the motor, the trigger being adapted to control operation of the motor in response to an input provided by an operator of the power tool by coupling the motor to a source of power; an output member; and a transmission coupling the motor and the output member; wherein the power tool is characterized by at least one of the following: (a) the transmission includes a first planetary stage and a second planetary stage, wherein the first planetary stage includes a planet carrier and a plurality of planet gears, the planet carrier comprising a plurality of pins onto which the planet gears are journally mounted, wherein the second planetary stage comprises a sun gear having an outer diameter onto which a plurality of sun gear teeth are formed, wherein the pins of the planet carrier are mounted to the sun gear radially inward of the sun gear teeth and wherein no portion of the sun gear that transmits torque is bigger in diameter than the outside diameter of the sun gear as measured across the sun gear teeth; (b) the transmission includes a first planetary stage and a second planetary stage, wherein the first planetary stage comprises a compound planet gear having a first ring gear, a second ring gear, and a first planet gear portion, which is meshingly engaged to the first ring gear, and a second planet gear portion that is coupled for rotation with the first planet gear portion and meshingly engaged with the second ring gear, and wherein the second planetary stage comprises a third ring gear that is axially movable between a first position, in which the third ring gear is meshingly engaged with a rotating component of the transmission, and a second position in which the third ring gear is disengaged from the rotating component; (c) the transmission includes a planetary stage having compound planetary gears with a first portion that is engaged to a first ring gear and a second portion that is engaged to a second ring gear, wherein the compound planetary gears are not timed to another gear in the transmission; (d) the transmission includes a planetary stage having a ring gear, a planet carrier and a plurality of planet gears, the planetary gears being meshingly engaged with the ring gear and journally supported on pins of the planet carrier, wherein adjacent ones of the pins are spaced apart by an angular spacing and wherein two or more different angular spacings are employed to thereby space the planet gears unevenly about the ring gear; (e) the power tool comprises a mode change mechanism having a cam, a cam follower, a planet gear and a ring gear, wherein the cam is rotatably mounted in the housing, the cam follower is engaged to the cam and non-rotatably but axially slidably mounted in the housing, wherein the planet gear is meshingly engaged with the ring gear and teeth formed on the cam, wherein rotation of the ring gear generates corresponding rotation or the cam to cause axial translation of the cam follower in the housing, wherein the cam follower is employed to selectively lock-out a torque clutch, position an axially movable hammer ratchet into a zone where it may be engaged by a rotary hammer ratchet that is mounted on the output spindle, or both; (f) the power tool comprises a spindle lock comprising a bushing that is coupled to an output member of the transmission at a first interface and to the output spindle at a second interface, at least one of the first and second interfaces being defined by a female portion and a male portion that is received in the female portion, the female portion being comprising a plurality of first V-shaped sidewalls that have peaks that face radially inwardly, the male portion comprising a plurality of second V-shaped sidewalls that are engaged the first V-shaped sidewalls, each of the first V-shaped sidewalls being defined by a first interior angle, each of the second V-shaped sidewalls being defined by a second interior angle that is smaller than the first interior angle to rotationally couple the female portion and male portion in a manner that provides limited rotational movement there between; (g) the power tool further comprises a clutch, the clutch having a plurality of follower members and a clutch spring, the follower members being received between a clutch profile on a ring gear of the transmission and the clutch spring, the clutch spring biasing the follower members into engagement with the clutch profile, wherein the clutch spring is an annular wave spring having a non-linear spring rate and preferably, a non-linear spring rate in which a plot depicting a load exerted by the clutch spring as a function of clutch spring deflection has a distinct knee between a first portion, which is generally defined by a first spring rate, and a second portion that is generally defined by a second spring rate that is greater than the first spring rate; (h) the power tool further comprises a torque clutch and a clutch bypass member, the torque clutch comprising a clutch profile, which is coupled to a ring gear of the transmission, and a follower member that is biased into engagement with the clutch profile to resist rotation of the ring gear when a magnitude of the torque output from the power tool does not exceed a clutch torque, the clutch bypass member comprising a plurality of lugs that are non-rotatably but slidably engaged to the housing, the clutch bypass member being axially movable between a first position, in which lugs are axially separated from the ring gear, and a second position in which the lugs are received within the ring gear such that the lugs are positioned radially inwardly of the clutch profile; (l) the transmission includes a planetary stage having a ring gear, the ring gear being axially movable between a first position and a second position to cause a change in a speed ratio of the transmission, the power tool further comprising a spring that is mounted coaxially about the transmission to bias the ring gear into one of the first and second positions; and (j) the housing further comprises a gear case into which at least a portion of the transmission is received, and a plurality of frusto-conical features are formed onto the body and the gear case to align the two to a common rotary axis. 